Pulmonary Embolism Rule-out Criteria (PERC)
Enter vital signs and risk factor information for patients with low pretest probability of PE to decide whether further testing is necessary.
How to Use This Calculator
Confirm low pretest probability
PERC applies only when clinical gestalt or validated scores estimate ≤15% chance of PE.
Enter vital signs and risk factors
Ensure accurate heart rate, oxygen saturation, and documentation of hemoptysis, estrogen use, prior VTE, leg swelling, and recent surgery.
Decide on further testing
PERC-negative patients can forego D-dimer testing; PERC-positive patients require standard diagnostic pathways.
Formula
PERC-negative requires: Age <50, Heart rate <100 bpm, SpO₂ ≥95% on room air, No hemoptysis, No exogenous estrogen, No prior DVT/PE, No unilateral leg swelling, and No recent surgery/trauma requiring hospitalization within 4 weeks.
Full Description
The PERC rule streamlines evaluation of suspected pulmonary embolism in low-risk emergency department patients. When all eight criteria are negative, the post-test probability of PE is sufficiently low to avoid D-dimer testing. Incorrect application to higher-risk patients can miss clinically significant emboli; always integrate with clinical judgement and local protocols.
Frequently Asked Questions
Can I apply PERC if the patient is hypoxic on supplemental oxygen?
PERC requires room-air SpO₂ ≥95%. Supplemental oxygen invalidates the criterion; treat as PERC-positive.
What if clinical suspicion remains high?
Do not use PERC in high-risk patients. Proceed directly to diagnostic testing based on Wells score or clinician judgement.
Is pregnancy a PERC exclusion?
Pregnancy was excluded from validation studies; PERC should not be used in pregnant patients.
How does PERC compare with age-adjusted D-dimer?
PERC prevents testing in very low-risk patients, whereas age-adjusted D-dimer refines interpretation for older adults requiring testing.